1. Field of the Invention
The present invention relates to pattern and object recognition, and more particularly to a method for detecting objects in a digital image.
2. Description of the Related Art
Over the years, there have been many methods developed to determine an image quality of an image-generating system such as a sensor/display combination. In many cases, the final consumer of the image produced is a human observer using their visual capability to extract visual information from the displayed image. In recent years, imaging systems and image manipulation have moved from the analog world to the digital world, which has probably added a bit more confusion to the issue of image quality or resolution.
In general, resolution is the ability of a sensor/display system to produce detail; the higher the resolution, the finer the detail that can be displayed. With the advent of digital imagery and sensor detectors that are comprised of an array of discrete elements, it is tempting, and not entirely incorrect, to characterize the resolution of the system by the number of picture element (Pixels) for the display or sensor elements in the case of the sensor. For example, SVGA resolution for a computer display is 600 elements high by 800 elements wide. This describes the number of samples that can be displayed; however, the number of pixels alone says nothing of the quality of the actual display medium characteristics (luminance, contrast capability, noise, color, refresh rate, active area to total area ratio, etc.) or of the signal/information used to feed the individual pixels. Nevertheless, this numerical value of pixel or sensor element count is often given as a primary metric to the resolution (quality) of the sensor or display.
Another common approach to determining the resolution of a sensor/display system is to image an appropriate resolution test target and determine the smallest sized critical test pattern element that can be seen by a human observer. Many test patterns have been developed over the years such as gratings, tri-bars, tumbling Es, the Snellen chart, and the Landolt C chart to test vision or to test imaging systems using vision. For these tests, a single size test element is generally imaged at various distances until a distance is obtained at which the test object is barely resolved. This multiple imaging method at multiple distances can be cumbersome and time consuming.
Accordingly, there is a need in the art for a device and process that will allow a rapid, fully automatic resolution assessment of optical sensors that operate individually or simultaneously over multiple spectra without the need for multiple images at multiple distances.